Coin type batteries or coin cells, as are commonly known, are used in numerous applications to power electronic circuits. A coin cell typically comprises small, usually round structure having a top conducting surface that acts as a first polarity electrode contact and a bottom conductive surface which acts as a second polarity contact. Typically the surfaces form the full upper and lower parts of the cell casing, are substantially co-extensive and extend substantially parallel to each other, spaced by the thickness of the cell. Coin type batteries are particularly useful to power electronic circuits in tight spaces where the use of a regular battery is not possible due to space limitations.
U.S. Pat. No. 4,487,820 issued to Engelstein et al on Dec. 11, 1984 describes a battery holder for a coin cell type battery that is intended for use in a printed circuit application where space appears to be at a premium. U.S. Pat. No. 5,922,489 issued to Adachi on Jul. 13, 1999 and U.S. Pat. 5,931,693 issued to Yamazaki on Aug. 3, 1999 are other examples of typical battery holders for coin cells.
A problem with such holders is that, even though they typically include asymmetrically located positive and negative contact electrodes, they do not prevent a reverse polarity voltage to be applied to the electronic circuit they power if the battery is inserted upside down into the holder. Such reverse polarity voltage may prove damaging to the electronic circuit and create a malfunction, or such contact may result in shorting the battery. A protection scheme described in U.S. Pat. No. 6,205,034, discloses electronic circuitry to sense current draw anomalies, yet still allows the battery to be inserted incorrectly and end up shorting itself.
There is, therefore, still a need for a simple and inexpensive scheme that will prevent an incorrectly inserted coin cell from damaging either the associated electronic circuit which it is intended to power or itself through accidental shorting.